Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
While the typical main CPU has a high performance, its power consumption is large. Use of the main CPU for a job that does not require high performance leads to waste of power, therefore a system that includes the main CPU and a sub CPU has been practically used. While the sub CPU does not have a high performance, its power consumption is small. According to this system, the main CPU and the sub CPU are selectively used in accordance corresponding to a job.
If an abnormality occurs in an operating voltage that is supplied to the CPU (for example, drop of the operating voltage and instantaneous interruption of the operating voltage), which causes the CPU malfunctions, a reset unit resets the CPU. In the system that includes the main CPU and the sub CPU, there is provided a technique that resets both the main CPU and the sub CPU to secure a synchronicity of processes of both of them when the reset unit resets at least one of the main CPU and the sub CPU based on a command of the main CPU.